Tazio Mirandola

TOC:Hide

high priority

Turn on apache's mod_deflate . it will reduce the data to transfer up to 80%.ther's a CPU cost, thats why dfault is compression 6 over max 9. AddOutputFilterByType DEFLATE application/javascript text/css
Install APC to increase performance by 25-100% by removing compile times
sending gz-encoded data to web browsers that support compressed web pages via ob_gzhandler()
Do use error_reporting (E_ALL); during debug.
Profile your code. A profiler shows you, which parts of your code consumes how many time. The Xdebug debugger already contains a profiler. Profiling shows you the bottlenecks in overview

require_once() is expensive
Use full paths in includes and requires, less time spent on resolving the OS paths.
Do use full file paths in production environment over basename/fileexists/open_basedir to avoid performance hits for the filesystem having to hunt through the file path. Once determined, serialize and/or cache path values in a $_SETTINGS array. $_SETTINGS["cwd"]=cwd(./);
Do use require/include over require_once/include_once to ensure proper opcode caching.
Do serialize application settings like paths into an associative array and cache or serialize that array after first execution.

If a method can be static, declare it static. Speed improvement is by a factor of 4.
Unset your variables to free memory, especially large arrays.
Avoid magic like get, set, __autoload

Set the maxvalue for your for-loops before and not in the loop.
Do use foreach for looping collections/arrays.
Do not use functions inside of for loop, such as for ($x=0; $x < count($array); $x) The count() function gets called each time.

echo is faster than print. Use echo's multiple parameters instead of string concatenation.
Do use single quotes over double quotes.
See if you can use strncasecmp, strpbrk and stripos instead of regex
str_replace is faster than preg_replace, but strtr is faster than str_replace by a factor of 4

Error suppression with @ is very slow.
Close your database connections when you're done with them
If you need to find out the time when the script started executing, $_SERVER['REQUEST_TIME'] is preferred to time()

Do use ctype_alnum,ctype_alpha and ctype_digit over regular expression to test form value types for performance reasons.

Do use POST over GET for all values that will wind up in the database for TCP/IP packet performance reasons.

Do use PDO prepare over native db prepare for statements. mysql_attr_direct_query=>1
Do NOT use SQL wildcard select. eg. SELECT *

Do set Apache allowoverride to "none" to improve Apache performance in accessing files/directories.